Fuel injection system for diesel engine

ABSTRACT

A fuel injection system for a diesel engine has a plunger barrel with a fuel intake port and a plunger slidable axially in the barrel. A plunger operating cam has a pair of lobes for operating the plunger. During either the intake or the compression stroke, the cam advances the plunger to a first position blocking the port to inject fuel, after which the plunger retracts. At the end of the compression stroke, the cam advances the plunger further to a second position to block the port to inject fuel. A switching device is effective to rotate the plunger between a starting position and a running position. In the starting position, the peripheral surface of the plunger blocks the port during the two fuel injections strokes of the plunger and, in the running position, the plunger is rotated to a position where its peripheral surface blocks the port only upon the further advance of the plunger to the second position. The invention improvement comprises at least one fuel passage in the plunger connecting the peripheral surface to the inner end face of the plunger and communicating with the port, during starting of the engine, and in the second plunger position.

United States Patent Nagasawa [S4] FUEL INJECTION SYSTEM FOR DIESELENGINE [72] Inventor: Shigeo Nagasawa, Kyoto, Japan [73] Assignee:Milsubishi Jidosha Kogyo Kabushiki Kaisha, Tokyo, Japan 221 Filed: Dec.22, 1969 211 Appl. No.: 886,960

[451 Oct. 17,1972

688,003 2/1953 GreatBritain'. ..123/32.61

Primary ExaminerLaurence M. 'Goodridge Assistant Examiner-Ronald B. CoxAttorney--McGlew and Toren [57] ABSTRACT A fuel injection system for adiesel engine has a plunger barrel with a fuel intake port and a plungerslidable axially in the barrel. A plunger operating cam has a pair oflobes for operating the plunger. During either the intake or thecompression stroke, the cam advances the plunger to a first positionblocking the port to inject fuel, after which the plunger retracts. Atthe end of the compression stroke, the cam advances the plunger furtherto a second position to block the port to inject fuel.

A switching device is effective to rotate the plunger between a startingposition and a running position. In

the starting position, the peripheral surface of the 1 Claim, 14 Figuresfiec'ond step upon starting t a first step upon running [52] US. Cl..123/32 G, 123/179 L, 123/32 R [51] Int. Cl. ..F02b 3/00, F02n 17/00[58] Field of Search ..123/32.6, 32.61

[56] References Cited UNITED STATES PATENTS I 1,818,580 8/1931 Prestage..417/457 2,250,877 7/1941 Pischinger ..l23/32.61 2,306,364 12/1942Skaredoff ..123/32.61 2,713,310 7/1955 Muraszew ..l23/32.61 2,871,7962/1959 Dreisin et al. ..l23/32.6l 2,960,079 11/1960 Monnot et a1...l23/32.6l 3,339,848 9/1967 Geiger ..239/453 FOREIGN PATENTS ORAPPLICATIONS 393,875 8/1932 Germany 123/3261 607,230 .12/l934 Germany..123/32.61 851,520 10/1952 Germany ..123/32.61 360,980 4/1938 Italy..123/32.61 465,887 9/1951 ltaly ..l23/32.6l 514,011 10/1939 GreatBritain ..123/32.6l 532,094 1/1941 Great Britain 123/32.61- 610,09510/1948 Great Britain 123/32.61

Cum lift Z4 2 2 [a 1 First step upon starting 22 Ho 23d Com angle 9 23PA'T ENTEnnm 11 1972 saw 1 or .4

INVENTOR Shigeo Nogqsowo ATTORNEYS 1 (PriorfArt) FIGQZ (Pribr Art)IIIIIIA I I I I PAIENTEDnct I7 1972 2 e First step upon running Firststep 3 -7- -Second step upon starting upon I, t starting Com angle 9 22H0 Starting Ho 22 llb P no Ila Running llb 22 H 6 (Prior Art) a r uAnozzle needle valve hft 85655558'ompression top INVENTO/P P Crank angle(9. Shlgeo Nogosowo F|G.7 (PriorArt) by {M ATTORNEYS PATENTEDnm t 7 I972SHEET 3 0F 4 flecond step upon starting First step upon running 0m angle9 33 23 Starting 2 Ho EKRunning "g \23O I uwewm? Smgeo NogosowoATTORNEYS PATENTEDnm 17 I972 sum 1 or 4 FIG.

FUEL INJECTION SYSTEM FOR DIESEL ENGINE BACKGROUND OF THE INVENTION In aknown conventional diesel engine, it has been common practice to startfuel injection several degrees before the upper dead point (-l-3) in thecompression stroke and either upon starting or during running.

If the atmospheric temperature is low during starting, then, due to thefact that the entire engine is at a low temperature plus the fact thatthe temperature of the intake air is low, the air in a cylinder chambercannot obtain a sufficiently high temperature even though the air iscompressed. Consequently, the ignition lag is extended and, during theinjection period of several degrees before the upper dead point in thecompression stroke, the time in which the fuel droplet makes contactwith the high temperature air, within the compression chamber, isshortened. Thus, ignition of the fuel droplet becomes very difficult.

In another known type of diesel engine, prior to the fuel injection andseveral degrees before the upper dead point in the compression stroke,an auxiliary fuel injection is performed at the beginning of thecompression stroke. In this type of diesel engine, the overall weight ofinjection of the fuel is substantially constant either upon starting orupon running. The object of this type of diesel engine is to enhance theefficiency of the engine by improving the combustion conditions of thefuel, and also to facilitate control of the operation.

While this type of diesel engine has excellent starting characteristicsdue to the two-stroke auxiliary fuel injection, it has a disadvantage.Since the second step of auxiliary fuel injection follows the first stepand, since the amount of fuel injected in the first step is determinedby a cam lift of a plunger, it is impossible conveniently to adjust thetime of commencement of fuel injection in the second step withoutvarying the quantity of fuel injected in the first step, and withoutreplacing a plunger operating cam by a cam having a different contour.

SUMMARY OF THE INVENTION This invention relates to fuel injectionsystems for diesel engines, and, more particularly, to an improved fuelinjection system for a diesel engine greatly enhancing the startingperformance under low temperature conditions.

The invention is directed to an improvement upon the type of dieselengine fuel injection system mentioned above and involving auxiliaryinjection of fuel during starting. In this type of fuel injectionsystem, a plunger barrel has a fuel intake port and a plunger isslidable axially in the barrel. A cam operates the plunger and has camlobes peripherally spaced in such a manner that, after the plunger hasbeen advanced, during the intake stroke or the compression stroke, to afirst position, and retracted, the plunger, at the end of thecompression stroke, is advanced further to a second position. Aswitching device is operable to rotate the plunger through substantially180 between a starting position and a running position.

In the starting position, the fuel intake port is blocked by the plungerperipheral surface so as to carry out two fuel injection strokes duringthe movement of the plunger to the first position and to the secondposition, respectively. In the running position, the plunger is rotatedto a position in which the fuel intake port is blocked by the plungerperipheral surface, to effect fuel injection, only when the plunger ismoved to the second position.

In accordance with the invention, a flow passage is provided. in theplunger connecting the peripheral surface of the plunger with its innerend face within the barrel. In the starting position of the plunger,this flow passage communicates with the fuel intake port when theplunger is advanced to the mentioned second position. In the runningcondition of the engine, the plunger is rotated to a position in whichthe flow passage can no longer communicate with the fuel intake port.

The invention arrangement has the advantage that, even if theatmospheric temperature is too low for the intake air to obtain asufficiently high temperature, by setting the switching device at thestarting position, the fuel is mixed uniformly with the intake air for along time and then heated up in the first step of auxiliary fuelinjection, sothat the ignition lag is reduced to an extent that ignitionoccurs with certainty. The torque necessary for rotating the engine canbe produced in the second step of auxiliary fuel injection. Thereafter,during running of the engine while the temperature of the engine isincreased, fuel injection is performed only upon movement of the plungerto the second position, by switching the control or switching device tothe running position. Thus, the engine will run smoothly while the fuelis being injected exactly at the rate necessary for running.Furthermore, the rate of fuel injection, during running, may besubstantially reduced with respect to the rate of fuel injection duringstarting, thus preventing a reduction in thermal efficiency.

More particularly, the inner space of the barrel is connected to thefuel intake port, in the starting position of the plunger, between thetime the plunger attains its first position and the time the plungerattains its second position. Thus, the time of commencement of fuelinjection may be arbitrarilyadjusted, as well as the quantity ofinjection in the second step, by appropriately delaying the time atwhich the fuel intake port is blocked by the plunger peripheral surface,and without changing the contour of the cam.

An object of the invention is to provide an improved fuel injectionsystem for diesel engines.

Another object of the invention is to provide such a fuel injectionsystem for diesel engines in which the starting operation is greatlyimproved.

A further object of the invention is to provide such an improved fuelinjection system for diesel engines in which the rate of fuel injection,during running of the engine, may be substantially reduced with respectto the rate of fuel injection during starting of the engine, preventingany reduction in thermal efficiency.

Another object of the invention is to provide such a fuel injectionsystem for diesel engines in which the time of commencement of fuelinjection, as well as the amount of fuel injected in the secondauxiliary injection step, may be arbitrarily adjusted without varyingthe contour of a plunger operating cam or without changing the plungeroperating cam.

For an understanding of the principles of the invention, reference ismade to the following description of typical embodiments thereof asillustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a somewhat schematic longitudinal cross section view of aprior art fuel injection system for a diesel engine;

FIG. 2 is a view similar to FIG. 1 but illustrating a different form ofprior art fuel injection system;

FIG. 3 is a partial side elevational view taken along the line IIIIII ofFIG. 2, looking in the direction of the arrow;

I FIG. 4 is a longitudinal sectional view, to a larger scale, of aprincipal part of FIG. 2;

FIG. 5 is a schematic diagrammatic view of the fuel injection systemshown in FIG. 2;

FIG. 6 is a graphical illustration of the relation between the cam liftand the plunger upon starting and running respectively, of the systemshown in FIG. 2;

FIG. 7 is a graphical illustration of the operating principle of thefuel injection system shown in FIG. 2;

FIG. 8 is a schematic diagrammatic view of one embodiment of fuelinjection system, for a diesel engine, in accordance with the invention;

FIG. 9 is a somewhat graphical illustration of the relation between thecam lift and the plunger, upon starting and running, respectively, ofthe embodiment of the invention shown in FIG. 8;

FIG. 1 is a schematic sectional view of the principal part of anotherembodiment of the invention;

FIG. 11 is a view, similar to FIG. 10, illustrating a modified form ofthe invention;

FIG. 11A is a top plan view taken at right angles to FIG. 11;

FIG. 12 is an axial sectional view through a further embodiment of theinvention; and

FIG. 13 is a view, similar to FIG. 11, illustrating still anotherembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a known auxiliary chambertype of diesel engine, as illustrated in FIG. 1, when the air compressedin a main chamber b by an upward stroke of a piston a flows into anauxiliary chamber d through a communication port 0, the air withinchamber d is cooled due to the choke loss at low temperature of the port0. Thus, even at the end of the compression stroke, it is difficult forthe air within auxiliary chamber d to reach the ignition temperature.Therefore, during starting, the fuel spray injected from a fuelinjection pump e through a nozzle f into auxiliary chamber d must arrivein main chamber b by passing through auxiliary chamber d and port 0.However, since the speed of the air current flowing from main chamber bthrough port is rather high, it is nearly impossible for the fuel sprayto arrive in main chamber b against this air current. Accordingly, thestarting performance is very poor, in an auxiliary chambertype of dieselengine, at low atmospheric temperatures.

To enhance the starting performance, there is a known fuel injectionsystem for a diesel engine as illustrated in FIGS. 2 through 7. In thisfuel injection system, a main chamber 1 has a piston 2 reciprocabletherein, and main chamber 1 communicates with auxiliary chamber 4through a port or aperture 3. In addition, a nozzle 6 provided with anozzle needle valve is mounted on auxiliary chamber 4, and a fuelinjection I pump body 8 is connected to nozzle 6 through tubing 7.-

In fuel injection pump body 8, there is slidably fitted, for axialreciprocation, a plunger 12 provided with a notched step portion 11,plunger 12 being mounted beneath a delivery valve holder having adelivery valve 9. Plunger 12 is'arranged to be driven axially of body 8by means of a cam 13 which is rotated in synchronism with the rotationof the diesel engine.

A rack 14 meshes with teeth (not shown) on the outer periphery ofplunger 12, and rack 14 is coupled to one end 15b of a fork lever 15which is pivotally supported approximately at its center portion 15a.The other end 15c of fork lever 15 is in abutment with a sliding shaft16a of an adjusting mechanism 16. An arm 15d extends from center portion15a of fork lever 15,

and is coupled to an adjustment knob 0r lever 18 through a spring 17. Inaddition, fuel injection pump body 8 is provided with a start button 19.22 is a fuel intake port provided on plunger barrel 8a within pump body8.

In this fuel injection system, if adjustment'knob or lever 18 is presetto a starting position as shown in FIG. 5, and if start button 19, shownby a broken line in FIG. 4, is moved to the solid line position of FIG.4, a rack pin 20, projecting from rack 14, is released from a stop 21for movement of the rack from the running position to the startingposition. Thereby plunger 12 is rotated to a position where the upperportion 11a of the notched step portion or inner end face 11 of plunger12 is opposite fuel intake port 22.

Under these conditions, if the engine is rotated by means of a knownstarter device, which has not been illustrated, cam 13 is rotatedcounter-clockwise as viewed in FIGS. 2 and 3. Plunger 12 is displaced bya first cam lobe 13a from a lift L shown in the left half portion of theupper section of FIG. 6, to another lift L shown in the right halfportion of the upper section in FIG. 6. During this period of time, fuelintake port 22 is blocked by upper portion or projection 1 1a of theinner end face 11 of plunger 12. Thus, a first fuel injection step iscarried out to inject substantially one-half of the total amount of fuelto be injected. The timing for raising plunger 12 by means of the firstcam mold 13a is set at the end of the intake stroke or at the beginningof the compression stroke. Therefore, the fuel injected into auxiliarychamber 4 by the first fuel injection step flows into main chamber 1through port or aperture 3. During the compression stroke, this fuel issufficiently mixed with the intake air and is heated to a hightemperature.

When first cam lobe 13a passes by the lower end of plunger 12, plunger12 is lowered for a time to interrupt the fuel injection. Thereafter, asecond cam lobe 13b comes into contact with the lower end of plunger 12to raise plunger 12 and, upon arrival of the plunger at lift L a secondstep of the fuel injection is begun.

Meanwhile, the temperature tm, shown in FIG. 7, of the mixture gasconsisting of the mixed air and fuel within main chamber 1 becomeshigher than the temperature tp within auxiliary chamber 4. Thus, gaswithin main chamber 1 is more easily ignited than within auxiliarychamber 4. Furthermore, the fuel injected in the second step also flows,at least partially, into main chamber 1 in the period when the speed ofthe current 0) through aperture 3 is reduced, the fuel flowing throughaperture 3 burning with the mixture gas so that the explosion forcenecessary for starting may be obtained and thus the engine may bestarted very easily.

When the engine has obtained a predetermined rpm, sliding shaft 16aslides in the direction of the arrow in FIG. 5, under the influence ofcentrifugal force of a weight 16b of adjusting mechanism 16.Correspondingly, rack 14 is moved, through fork lever so that plunger 12is turned through 180 and the lower portion 11b of the notched inner endface of plunger 12 is opposite fuel intake port 22.

Under these conditions, even if plunger 12 arrives at lift 1,, due tofirst cam lobe 13a, fuel injection cannot be attained because fuelintake port 22 has not been blocked. It is only when plunger 12 arrivesat lift 1 due to second cam lobe 13b, that fuel intake port 22 isblocked by the lower portion 11b of the notched inner end face 11 ofplunger 12, to cause the fuel to be injected. Thus, fuel injection in asmaller quantity than during starting, and exactly similar to aconventional engine, is effected for enabling sustaining of a normalrunning operation.

In addition, even though the engine has not obtained a predeterminedrpm, if adjustment knob or lever 18 is set at the running position,plunger 12 is turned and an adjustment is made so that lower portion 11bof the inner end face 11 is opposed to fuel intake port 22.

In the known fuel injection system shown in FIGS. 2 through 7, byadjusting the height of the step portion of the inner end face 11 ofplunger 12, or the lift 1, and 1 of the cam lobes, or both, in variousmanners, the amount of fuel injected in the first step during startingcan be set at -75 percent of the total fuel injection amount, and thetotal fuel injection amount, during starting, can be set at 150-300percent of the total fuel injection amount for the maximum output uponrunning.

As mentioned the known fuel injection system shown in FIGS. 2 through 7,has a better performance, during starting, than a direct injection typeof engine, due to the fact that, upon starting, a first fuel injectionstep is effected at the beginning of the compression stroke when thespeed of the air current in aperture 3 is low, so that the fuel canenter in sufficient amount into main chamber 1 whereby ignition mayoccur in chamber 1 at a higher temperature than the temperature tp ofthe compressed air in auxiliary chamber 4.

However, since the second step of fuel injection is begun at the momentwhen plunger 12 rises again and has arrived at cam lift 1 after it hadinitially been lifted tothe level 1;, and then been retracted, and sincethe fuel injection amount in the first step is defined by the cam liftsl and I it is impossible conveniently to adjust the time of initiationof fuel injection in the second step without varying the fuel injectionamount in the first step and without replacing cam 13 by another camhaving a different contour.

Referring to FIGS. 8 and 9, in accordance with the present invention, afuel injection system, such as shown in FIGS. 2 through 7, is modifiedby providing a communicating flow path or passage extending from thelower portion 11b of the inner end face of plunger 12 downwardly andthen laterally to the peripheral surface of plunger 12, and opposingfuel intake port 22 in the starting state of the parts. In thisconnection, the opening 23a of passage 23, on the plunger peripheralsurface, is provided at a level such that it may be opposite fuel intakeport 22 at the position of cam lift 1 Since the embodiment of theinvention shown in FIGS. 8 and 9 is constructed in this manner, in caseplunger 12 is set, during starting, so that the upper piece 11a of itsnotched stepped inner end face 11 is opposite fuel intake port 22, then,as illustrated in the upper half portion of FIG. 9, at the positionwhere the cam lift 1 is obtained by first cam lobe 13a, the upper spacewithin barrel 8a and fuel intake port 22 are connected with each otherthrough passage 23. Thus, even if plunger 12 is raised somewhat upwardlyfrom the level of cam lift 1 bythe second cam lobe 13b, the second stepof the fuel injection is not commenced until opening 23a on theperipheral surface of plunger 12 has been displaced upwardly from fuelintake port 22 to the position of cam lift 1 At the position of cam lift1 communication between the upper space within barrel 8a and fuel intakeport 22 is interrupted, whereby the second fuel injection step iscommenced.

However, and as illustrated in the lower half portion of FIG. 9, in theposition of the parts in which plunger 12 is turned through 180 to beswitched to the running state, as opening 23a of passage 23 is directedaway from fuel intake port 22, the time of initiation of fuel injection,as well as the amount: of injection during running, do not differ fromthose inherent with the omission of flow passage 23, and are thusmaintained constant.

In the embodiment of the invention shown in FIGS. 8 and 9, it ispossible to adjust the time of initiation of fuel injection, as well asthe quantity of fuel injected, in the second step in the starting state,and in a very simple and easy manner by varying the diameter, the heightor both, of the opening 23a on the peripheral surface of plunger 12, andwithout modifying the shape of cam lobes 13a and 13b. Thereby, there isobtained fuel injection upon starting which is most suitable for thevarious characteristics of the engine such as, for example, startingcharacteristics, output power, noise, etc., thus toenhance theperformance of the engine.

In the embodiment of the invention shown in FIGS. 8 and 9, a notchedstep portion 11 is provided. However, the same function and advantagecan be obtained when the upper or inner end face of plunger 12 is cutobliquely as shown in FIG. 10, and flow passage 23 is formed so as todispose opening 23a at the side toward the higher end of the oblique endface of plunger 12.

Alternatively, instead of providing different top levels of plunger 12on the respective sides, by forming the top face of plunger 12 in aplane perpendicular to the axis of the plunger, while providing aplurality of fuel intake ports 22 on barrel at different levels, fittinga sleeve around the outer periphery of barrel 8a so as to be freelydisplaced in the axial and circumferential directions, and selectivelydisplacing an opening formed in the sleeve to a position opposed to oneof the plurality of fuel intake ports 22, there can be achieved two stepinjection upon starting and one step injection during running.Furthermore, although a single flow passage 23 has been shown in theillustrated embodiments, if desired two or more flow passages may beprovided.

FIG. 11 and 11A illustrate an embodiment of the invention in which twoaxially spaced radial ports 23a and 23b communicate with passage 23.Referring to FIG. 12, an embodiment of the invention is illustratedincluding a sleeve 123 provided with a port 123a which is selectivelyregisterable with any one of three angularly and'axially spaced ports22a, 22b and 220 in barrel 22. Sleeve 123 is both rotatable and axiallydisplaceable relative to barrel 22.

The arrangement of FIG. 13 is substantially similar to that of FIGS. 11and 11A, except that three ports 23a, 23b and 23c are provided and arespaced axially from each other.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. ln a fuel injection system for a diesel engine, of the type includinga plunger barrel having a radial fuel intake port, a plunger slidableaxially in the barrel, a plunger operating cam having peripherallyspaced lobes engageable with the plunger and operable, during one of theintake and compression strokes, to advance the plunger to a firstposition to block the port to inject a first quantity of fuel and thento provide for plunger retraction to free the port, the cam, at the endof the compression stroke, advancing the plunger further to a secondposition to block the port to inject a second quantity of the same fuel,and a switching device effective on the plunger, only during starting ofthe engine, to position the plunger so that its peripheral surfaceblocks the port during advance of the plunger to the first and secondpositions, to effect two injections of the same fuel, and only duringrunning of the engine, to position the plunger so that its peripheralsurface blocks the port, for a single injection of the same fuel, onlyupon advance of the plunger to the second position, the improvementcomprising at least one flow passage in said plunger connecting saidperipheral surface of said plunger to the inner end face of said plungerand communicating with said port, only during starting of the engine, insaid second plunger position; a plurality of fuel intake ports in saidbarrel at different levels; and a sleeve enclosing said barrel anddisplaceable axially and circumferentially thereof; said sleeve havingan opening therein cooperable with a selected one of said fuel intakeports.

I! i I!

1. In a fuel injectioN system for a diesel engine, of the type includinga plunger barrel having a radial fuel intake port, a plunger slidableaxially in the barrel, a plunger operating cam having peripherallyspaced lobes engageable with the plunger and operable, during one of theintake and compression strokes, to advance the plunger to a firstposition to block the port to inject a first quantity of fuel and thento provide for plunger retraction to free the port, the cam, at the endof the compression stroke, advancing the plunger further to a secondposition to block the port to inject a second quantity of the same fuel,and a switching device effective on the plunger, only during starting ofthe engine, to position the plunger so that its peripheral surfaceblocks the port during advance of the plunger to the first and secondpositions, to effect two injections of the same fuel, and only duringrunning of the engine, to position the plunger so that its peripheralsurface blocks the port, for a single injection of the same fuel, onlyupon advance of the plunger to the second position, the improvementcomprising at least one flow passage in said plunger connecting saidperipheral surface of said plunger to the inner end face of said plungerand communicating with said port, only during starting of the engine, insaid second plunger position; a plurality of fuel intake ports in saidbarrel at different levels; and a sleeve enclosing said barrel anddisplaceable axially and circumferentially thereof; said sleeve havingan opening therein cooperable with a selected one of said fuel intakeports.